Abandonment of a Flowing, Corroded Irrigation Well
A 12-inch steel-cased irrigation well was drilled in 1958 to 180 ft. It has 40 ft of slotted screen from 130 to 170 ft, a corroded casing section at 20–30 ft, and flows about 5 gpm at the surface. Static water is 10 ft below grade; a shallow domestic well is 40 ft away. The flow increases after heavy rain. The landowner plans to convert the site to a vineyard and wants the well simply capped. The county requires destruction under California well standards and a report. The driller has neat cement, bentonite, gravel, a 20-ton rig, a tremie, and a packer. No original log is available and access is limited.
1. Lay out the destruction plan, including flow control and the final plug.
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Do not cap it. A cap leaves a 180-ft open conduit with a corroded casing and an artesian flow, so it can move water between aquifers and leak at the surface. Plan: notify the county and confirm the permit; remove the pump and any obstructions; video or tag the casing to locate the screen and corrosion; clean the well. Control the 5-gpm flow with a packer set below the corroded section or with weighted mud, but do not leave mud as the final seal. Fill from the bottom up with neat cement or cement-bentonite grout through a tremie, displacing the water and sealing the screen interval first. If the flow cannot be stopped, use a packer and pressure grout in stages, with a bleed tube to relieve water while the grout sets. Fill to at least 5 ft below grade, cut the casing at least 5 ft below grade, and place a concrete cap. Gravel is not a final plug because it is permeable.
2. What is the cross-connection risk to the domestic well 40 ft away, and how does the flowing condition change the job?
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The flowing well is an artificial connection between a deeper artesian aquifer and the shallow aquifer used by the domestic well. The corroded casing at 20–30 ft and the open screen at 130–170 ft mean water can move vertically outside the casing or through the casing if it is breached. A 40-ft separation is close enough that a failed seal or a poorly grouted abandonment could change the domestic well's water level or quality. The flow also makes placement harder: grout can be diluted or pushed out, and a cap can be blown off. That is why the plan uses a packer or staged grouting and a tremie, not a dump-and-cap approach. The domestic well should be monitored before and after, and the county should be told if its water level or turbidity changes.
3. What records and notifications are required, and how do you proceed without the original log?
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File the county destruction permit and the DWR well report; keep the contractor's records of casing size, total depth, screen interval as found, grout materials, volumes, and final plug depth. Notify the county before work and after completion. Without the original log, do not guess the screen depth: video the well or tag it with a weighted line, and if the screen cannot be located, fill the entire borehole with cement rather than leaving an unsealed interval. Document the method used to find the screen. If the casing is too corroded to video, treat the whole hole as open and grout from bottom to top. The report should state that the original log was unavailable and describe the actual conditions found.